The present invention relates to a mechanical fastener suitable for use on a disposable absorbent article. More particularly, the present invention relates to a cloth-like mechanical fastener having improved flexibility and to methods by which such a fastener can be made.
It is desired that mechanical fasteners have the ability to provide reliable yet comfortable securement of garments. Moreover, it is desirable that such mechanical fasteners be provided on a flexible material. The fastening material is desirably embedded within the flexible material to help present a cloth-like surface to the wearer or the caregiver and to reduce the possibility of the fastener having exposed harsh edges. In certain circumstances, it is also desirable that such fasteners include multiple discrete areas of mechanical fastening material to further enhance the flexibility of the fastener and reduce the possibility of creasing the rigid fastener material. This is particularly useful if the fastener is being used in combination with a garment to be worn by an active wearer. As such, it is desirable that the fastener be capable of being bent or conformed to better accommodate an active wearer while reducing the potential of creasing the rigid fastener material in order to avoid the creation of harsh, rough edges. In such circumstances, it is also desirable for the perimeter of the mechanical fastening material to be surrounded by the flexible material to further ensure the comfort of the wearer when the mechanical fastener is in use. Such fasteners can be advantageously provided for use on absorbent articles such as diapers, diaper pants, training pants, incontinence garments, feminine hygiene products, wound dressings or the like.
In general, the term xe2x80x9cmechanical fastenersxe2x80x9d may include hooks, snaps, buttons, zippers and other means. Specifically, the xe2x80x9cmechanical fastenersxe2x80x9d of subject invention are what are commonly referred to as xe2x80x9chook-and-loopxe2x80x9d fastener systems. Some hook-and-loop systems employ hooks attached to a non-woven, woven, or knitted fabric backing. These systems, with hooks attached to a fabric backing find utility in various textile and durable applications, may be flexible, but are generally rather harsh and are too expensive for use in disposable absorbent products. More specifically, the focus of this invention is on hook-and-loop fastener systems wherein the xe2x80x9chooksxe2x80x9d are directly attached to a more or less continuous polymer film or billet.
Typically, mechanical fasteners do not have a flexible backing material. Mechanical fasteners have conventionally had relatively thick and rigid backing materials that are prone to creasing. The creases, in combination with the harsh edges of the fastener material itself, may lead to red-marking or irritation of the wearer""s skin. For example, mechanical fasteners currently used on absorbent articles typically include a single area of fastening material with a backing material that is several times thicker than the material used for the outer cover of the absorbent article. Typically, the outer cover film material is 10 to 20 xcexcm thick. The backing material of mechanical fasteners is typically in the range of from about 50 to about 300 xcexcm thick. Moreover, the mechanical fastening material is not recessed within the film backing material, thereby exposing the rigid edges of the fastening material.
In the past, absorbent articles have been constructed to include isolated areas or patches of hook fastening material for securement within the article itself or for securement of the article to a garment. While the hook fastening material of such articles may have been configured into discrete areas, the hook fastening material was not recessed around its edges into the surrounding material (such as a nonwoven material). Therefore, such articles still had the potential for harsh edges of fastening material to be exposed. The existing art has also recognized the need to somehow buffer the edges of hook fastening materials. For example, fastening materials having a base with feathered selvedge edges have been described. The thickness of the base gradually decreases from a nominal value to a minimum value over the width of the feathered selvedge edges. Such art, however, does not describe recession of the base edges into a surrounding material.
Accordingly, there remains a need for hook and loop type mechanical fastener systems that can provide the benefits of flexibility, softness, simplicity of manufacture and a cloth-like presentation. That is, there remains a need for mechanical fasteners that are provided on a flexible layer, that have the rough edges of the fastener material recessed within a flexible layer, and that can be bent or altered with reduced creasing. Such a fastener would improve the comfort of the wearer by better accommodating the wearer and providing a pleasing cloth-like feel in use. Moreover, there is a need for improved methods of reliably and consistently making disposable absorbent articles with such mechanical fasteners.
In response to the difficulties and problems discussed above, new mechanical fasteners, and methods by which fasteners can be made have been discovered. The mechanical fasteners of the present invention provide several benefits including a more cloth-like presentation, decreased likelihood of creasing and reduced risk of skin irritation. While the fasteners of the present invention can have a variety of applications, the fasteners are particularly beneficial when used in conjunction with absorbent articles such as diapers, incontinence garments, training pants and diaper pants. The purposes and advantages of the present invention will be set forth in and apparent from the description that follows, as well as will be learned by the practice of the invention. Additional advantages of the invention will be realized and attained by the fasteners and methods particularly pointed out in the written description and claims hereof, as well as from the appended drawings.
In one aspect, the present invention concerns a mechanical fastener that defines a fastener longitudinal direction, a fastener lateral direction, and a third direction. The fastener longitudinal direction is the direction that is parallel to the centerline of an absorbent article when a fastener is attached to an absorbent article and generally corresponds to the xe2x80x9cyxe2x80x9d direction of the fastener. The fastener lateral direction is the direction that is perpendicular to the centerline of an absorbent article when a fastener is attached to an absorbent article and generally corresponds to the xe2x80x9cxxe2x80x9d direction of the fastener. The third direction is the direction that is perpendicular to the plane defined by both the fastener lateral direction and the fastener longitudinal direction, and generally corresponds to the xe2x80x9czxe2x80x9d direction of the fastener. The fastener comprises a flexible layer and at least one discrete fastener island. The fastener island has a planar perimeter edge, a mechanical fastening material, and a backing material attached to the mechanical fastening material. The backing material is embedded within the flexible layer and the planar perimeter edge is surrounded by the flexible layer. The planar perimeter edge is the outermost edge of the fastener island along a plane defined by the lateral and longitudinal direction, and is perpendicular to the third direction. As such, the planar perimeter edge defines the edge of the fastener island at its largest cross section.
The flexible layer may be constructed of a fabric, for example, a nonwoven material. Other suitable materials for the flexible layer include knit or woven fabrics, foams and reticulated films. Various types of nonwoven materials may be advantageously used as the flexible layer, such as a thermally or chemically bonded carded web or a nonwoven laminate. Examples of nonwoven laminates that may be advantageously used as the flexible layer include stretchable neck bonded laminates, such as those disclosed in U.S. Pat. No. 5,789,065 issued on Aug. 4, 1998 to Haffner et al. and U.S. Pat. No. 5,336,545 issued on Aug. 9, 1994 to Morman. Alternatively, relatively inelastic nonwoven laminates, such as a spunbond/meltblown/spunbond composite may also be advantageously used. When the flexible layer is provided by a nonwoven material, the flexible layer is generally soft to the touch and provides a cloth-like sensation to the wearer and the caregiver, as nonwoven materials are desirably comprised of fine fibers. The flexible layer may be extensible or stretchable, meaning that the layer is capable of extending to a greater length or width upon application of a force. Moreover, the flexible layer may define a particular thickness in the third direction, for example from about 250 to about 2500 xcexcm.
The mechanical fastening material may consist of a hook material, and further, the hook material may contain multiple hooks. For example, the hook material may contain at least 20 hooks. The number of hooks can also be described in terms of a hook density (number of hooks per square centimeter). It is possible to fabricate hook material having a hook density of from about 60 hooks/cm2 to about 1600 hooks/cm2. More desirably, the hook material has a hook density of from about 100 hooks/cm2 to about 750 hooks/cm2. The term xe2x80x9chookxe2x80x9d should be understood to encompass various geometries of protuberances that are suitable for engaging into a loop material or a material having loop characteristics in order to place or secure a fastener. Exemplary geometries include prongs, stems, trees (such as the shapes connoted by xe2x80x9cevergreenxe2x80x9d and xe2x80x9cpalmxe2x80x9d trees), mushrooms, J-hooks, bi-directional hooks and studs protruding at various angles. In addition to the various possible geometries of hooks, the hooks may protrude from a backing material at various angles. U.S. Pat. No. 5,782,8199 issued to Tanzer et al. on Jul. 21, 1998 describes a fastener system that includes velvet fabrics as examples of materials exhibiting differential friction. The surface of velvet fabric has fibers protruding from the surface, oriented on a bias. Despite the fibers being essentially straight (i.e. without barbs or hooks), they engage an opposed surface and facilitate fastening. The discrete hooks of the hook material may include or be treated with materials such as soft rubbers that increase the coefficient of friction of the hooks against the corresponding loop/engaging material. The increased coefficient of friction serves to reduce the tendency of the fastener to pop-open under stress. The benefits of fasteners having increased coefficients of friction are described in U.S. patent application Ser. No. 09/705,512 entitled xe2x80x9cHook and Loop Fastener Having an Increased Coefficient of Frictionxe2x80x9d filed by Martin et al. on Nov. 3, 2000.
The backing material attached to the fastening material may be embedded in the flexible layer by ultrasonic or thermal bonds or by adhesive. In addition, the fastener may include a plurality of discrete fastener islands.
Further, the flexible layer of the mechanical fastener may include a first flexible layer and a second flexible layer. The first flexible layer may define an interior surface and an exterior surface where the backing material of the fastener island can be attached to the interior surface of the first flexible layer. The second flexible layer is also attached to the interior surface of the first flexible layer where the second flexible layer defines an opening that corresponds to the discrete fastener island and exposes the mechanical fastening material of the discrete fastener island. Accordingly, the first and second flexible layers are stacked flush upon each other in the third direction, with the second flexible layer providing an opening through which the mechanical fastening material of the discrete fastener island is exposed.
Finally, the mechanical fastener may also have a user""s end and a bond end. The bond end can be permanently attached to a disposable absorbent article and the user""s end contains the discrete fastener island. The user""s end can also be configured to secure the disposable absorbent article about a wearer.
In another aspect, the present invention concerns a mechanical fastener that defines a fastener longitudinal direction, a fastener lateral direction, and a third direction. The fastener also includes a nonwoven layer and a plurality of discrete fastener islands. The discrete fastener islands have a planar perimeter edge, a mechanical fastening material and a backing material attached to the mechanical fastening material. The backing material of each of the discrete fastener islands is embedded within the nonwoven layer and the planar perimeter edge of each of the discrete fastener islands is surrounded by the nonwoven layer.
The planar perimeter edges of the plurality of fastener islands may have various shapes, such as circular. Other suitable shapes may include, but are not limited to, square, triangular, oval, linear, and the like, or combinations thereof. The nonwoven layer may be provided by a variety of nonwoven materials such as a thermally or chemically bonded carded web, a nonwoven or a laminate of nonwovens including neck bonded laminates, as well as spunbond/meltblown/spunbond composites. The nonwoven layer may be extensible or stretchable as described previously. Moreover, the nonwoven layer may define a particular thickness in the third direction, for example from about 250 to about 2500 xcexcm.
As with the previously described aspect of the invention, the mechanical fastening material may consist of a hook material, and further, the hook material may contain multiple hooks. For example, the hook material may contain at least 20 hooks. In addition, the hook material may be constructed of flat top hook material. The backing material attached to the fastening material may be embedded in the flexible layer by ultrasonic bonds.
Further, the nonwoven layer of the mechanical fastener of this aspect of the invention may include a first nonwoven layer and a second nonwoven layer. The first nonwoven layer may define an interior surface and an exterior surface where the backing material of the discrete fastener islands can be attached to the interior surface of the first nonwoven layer. The second nonwoven layer is attached to the interior surface of the first nonwoven layer where the second nonwoven layer defines an opening that corresponds to the discrete fastener islands and exposes the mechanical fastening material of the discrete fastener islands. Accordingly, the first and second nonwoven layers are stacked flush upon each other in the third direction, with the second nonwoven layer providing openings through which the mechanical fastening material of the discrete fastener islands are exposed.
Finally, the mechanical fastener may also have a user""s end and a bond end. The bond end can be permanently attached to a disposable absorbent article and the user""s end contains the discrete fastener islands. Accordingly, as the user""s end contains the fastener islands, the user""s end is configured to secure the disposable absorbent article about a wearer. Alternatively, the mechanical fastener may be integral to the absorbent article; that is, the flexible layer of the mechanical fastener may be an extension of the outer cover, bodyside liner or other component of the main body of the absorbent article. An example would be an absorbent article that includes an integral belt element. The ends of the belt element may include the flexible layer of the mechanical fastener. In another alternative, the mechanical fastener may be located on an attachment panel in either a front or rear waist portion of the absorbent article. A loop or other engaging material is then located integral with or attached to the outer cover. The loop material is located on a portion of the article that extends laterally away from the longitudinal centerline of the article. The loop material portion or portions are then wrapped around the waist of the wearer so as to engage the mechanical fastener located on the attachment panel of the article.
The number and configuration of fastener islands on the fasteners of the invention can vary. A moderate number of fastener islands on a fastener can range from to 2 to about 16; a large number of fastener islands on a fastener would be a number greater than about 16. In addition to the number of fastener islands, the total hook area accumulated by the fastener islands will affect the cost, flexibility, grip, skin friendliness and ease of manufacture of the fasteners. A low hook area is an area of about 2 cm2 or less; a high hook area is an area of about 8 cm2 or more; a moderate hook area is an area between about 2 cm2 and about 8 cm2. Having a relatively low number of islands combined with a low hook area provides a fastener having low manufacturing cost, high flexibility, low grip and skin friendliness. Increasing the hook area to a moderate hook area increases the cost and improves the grip of the fastener; using a high hook area with a low number of islands would have a further increased cost. Having a relatively large number of islands combined with a low hook area provides a fastener having low manufacturing cost, high flexibility, low grip and skin friendliness but also being relatively more difficult to manufacture at high speeds. Increasing the hook area to a moderate hook area increases the cost and improves the grip of the fastener; using a high hook area with a large number of islands would have an even higher cost and could have decreased skin friendliness. Based on a balancing of the relevant factors, it is desirable for a fastener to have a relatively low number of fastener islands and a moderate total hook area (the area of hooks not including the xe2x80x9cseaxe2x80x9d areas between the fastener islands). Such fasteners provide the benefits of moderate cost, high flexibility, strong grip and skin friendliness.
The spacing between fastener islands can range from about 3 mm to about 30 mm. The fastener islands can be arranged in any suitable geometry including a xe2x80x9ccheckerboardxe2x80x9d pattern, a chevron pattern and around the perimeter of an oval or other shape. For some fasteners, it may be desirable to arrange the fastener islands to create well-defined lines of flexibility by leaving xe2x80x9clinesxe2x80x9d free of fastener islands. For other fasteners, it may be desirable to arrange the fastener islands to block lines of flexibility.
In yet another aspect, the present invention concerns a disposable absorbent article that includes an outer cover, a bodyside liner, an absorbent core located between the bodyside liner and the outer cover, and at least one mechanical fastener. The mechanical fastener includes a nonwoven layer and a plurality of discrete fastener islands. The discrete fastener islands have a planar perimeter edge and a mechanical fastening material. A backing material is attached to the mechanical fastening material. The backing material of each of the discrete fastener islands is embedded within the nonwoven layer and the planar perimeter edge of the discrete fastener islands is surrounded by the nonwoven layer. The mechanical fastener is configured to refastenably secure the disposable absorbent article about a wearer.
The mechanical fastening material of the fastener on the disposable absorbent article may be a variety of fastening materials including a hook material. In addition, the mechanical fastener can be configured to refastenably engage directly to the outer cover of the absorbent article. Alternatively, the disposable absorbent article can also include an attachment panel, where the fastener is configured to refastenably engage the attachment panel. Conversely, the fastener can be located on the attachment panel and can be configured to refastenably engage another portion of the article having a complementary engagement material.
In still another aspect, the present invention concerns a fastener made by a process including the step of providing a continuous nonwoven web. This is followed by a step of intermittently applying drops of a molten polymer to the nonwoven web. Suitable polymers include polypropylene, and other polyolefins, nylons, aromatic and aliphatic polyesters including polylactic acid-based polymers, polyurethanes, natural and synthetic rubbers, proteins and other polymers. The process continues with a step of molding the drops of molten polymer into a plurality of discrete fastener islands to provide a backing material and a mechanical fastening material in each of said discrete fastener islands. The process concludes with a step of chilling the discrete fastener islands, and embedding the backing material within the nonwoven web to provide a continuous web of mechanical fasteners. The molten polymer may be molded and chilled by using a combination of a rotary die and a pressure roller. The rotary die may be configured to mold the molten polymer while being internally cooled to chill the molten polymer, thereby embedding it within the nonwoven web.
The mechanical fastening material of the mechanical fastener produced by this process can be hook fastening material. Moreover, the nonwoven web can be a neck bonded laminate web or a thermally bonded carded web. Further, the mechanical fasteners produced by the process described above may be configured to be nested within an adjacent fastener in the continuous web of mechanical fasteners. U.S. Pat. No. 5,876,531 issued to Jacobs et al. on Mar. 2, 1999 describes such a process for making mechanical fasteners. Accordingly, in such a configuration, the fasteners fit within the negative space created when the adjacent fastener is cut from the nonwoven web without any wasted nonwoven materials. Finally, the mechanical fastener may also be produced by a process that further includes the step of cutting individual fasteners from the continuous web of mechanical fasteners or the process could further include the step of winding the continuous web of fastener.
The present invention advantageously provides cloth-like mechanical fasteners and methods by which cloth-like mechanical fasteners can be made. In particular, the present invention includes mechanical fasteners that provide reliable securement of absorbent articles upon a wearer while still being flexible and providing a cloth-like presentation to the wearer and others coming into contact with the fasteners. Moreover, the mechanical fasteners of the present invention provide a mechanical fastening area that is recessed within the flexible layer, reducing the possibility of exposing any rigid edges of the fastening material that may be present. In addition, due to the refastenable nature of the fasteners of the present invention, the fasteners may be applied and re-applied to adjust and improve the fit of the article upon the wearer. Moreover, skin irritation in the user of the fastener during repeated application and reapplication of the fasteners may be reduced, because the embedding of the fastener islands shields the user and the wearer from the potentially harsh fastening material. Accordingly, wearer and caregiver comfort is enhanced. Reducing the occurrence and severity of skin irritation on areas of skin covered by absorbent articles or other sensitive areas is particularly important as the skin in these areas are more susceptible to the discomfort of inflammation. In certain configurations, the mechanical fastener of the present invention is particularly capable of being bent or conformed without producing harsh creases in the mechanical fastening material. This flexibility heightens the soft, cloth-like presentation of the fastener of the present invention to the wearer and the caregiver. Moreover, this flexibility also provides improved fit and comfort to the wearer by allowing the fastener to better conform to the body of the wearer and better accommodating the movement of the active wearer.
An additional benefit of a fastener that more closely conforms to the body of the wearer is more reliable fastening. It is often desirable to provide a soft and flexible loop portion as part of a hook and loop fastening system. When using a soft and flexible loop portion, the hook portion of the fastener is desirably selected so as not to compromise the security of the fastening system. If the hook and loop portions are mismatched, the softer portion will gently fold when subjected to external forces and the more rigid portion may form sharp creases. When this occurs, the external forces tend to pull the hooks away from the loops leading to failure (a.k.a. xe2x80x9cpop opensxe2x80x9d). The soft, flexible hook portions of the present invention are more suitably matched with soft, flexible loop portions to provide improved security. Thus, the fastener of the present invention improves the fit and comfort of the garment, and additionally reduces the occurrence of irritation and red-marking of the wearer""s skin.
An additional benefit of the present invention is that the cloth-like presentation of the fastener provides opportunities for improved aesthetics. The flexible layer may be printed with any desired pattern and the fastener islands may be colored in such a way that they either blend with or contrast with the flexible layer. When the fastener islands visually contrast with the flexible layer, they can be arranged to give an attractive geometric or cartoon-like impression.
It is understood that both the foregoing general description and the following detailed description are exemplary and are intended to provide further explanation of the invention claimed. The accompanying drawings, which are incorporated in and constitute part of this specification, are included to illustrate and provide a further understanding of the fasteners and processes for making fasteners of the present invention. Together with the description the drawings serve to explain the various aspects of the invention.